Origin of massive high-velocity stars in the halo

晕中大质量高速恒星的起源

• 批准号: 386788844
• 负责人: Professor Dr. Ulrich Heber
• 金额: --
• 依托单位: Astronomisches Rechen-Institut
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2017
• 资助国家: 德国
• 起止时间: 2016-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/386788844?language=en
• 关键词: Origin; massive; velocity; stars; halo

Twelve years after their serendipitous discovery in 2005, hyper-velocity stars (HVSs) are more than ever a hot topic and interest will be boosted in the Gaia era which started right now. These objects are late B-type stars that move with very high velocities through our Galaxy, and most of them are even gravitationally unbound to our Milky Way. Initially, the dynamical interaction with the supermassive black hole in the Galactic centre (GC) was their only suggested origin. In the meantime, however, more and more massive high-velocity stars were found that did not originate in the GC and thus challenged this picture. Those stars are extreme cases of so-called runaway stars, a well-known group of kinematically peculiar stars which can be ejected from their environment by dynamical interactions in star clusters or by a supernova explosion disrupting a binary system. An extragalactic origin from the Large Magellanic Cloud or disrupted dwarf satellite galaxies is also considered possible. Our work during the past couple of years has revealed strong links between runaway stars and HVSs. Consequently, trying to understand the one class of stars requires to understand the other class as well. Therefore, we had extended our research projects to a broad range of high-velocity stars. The goal of this project is to understand the origin and nature of massive runaway and HVSs. This requires a combination of quantitative spectroscopic and astrometric/kinematic analyses. Improved model atmospheres and novel spectral diagnostic tools derived in our team shall be applied to high fidelity optical spectra, partly already at hand. Gaia astrometry will be the backbone of the project. These data can be utilized, for example, to improve Galactic mass models and to trace back stellar trajectories to their places of origin. Furthermore a complete sample of high-velocity stars can be established to test population synthesis models. The places of origin as well as the ejection mechanisms will be identified from chemical tagging combined with the information from Gaia astrometry.

在2005年偶然发现的十二年后，超速级明星（HVSS）比以往任何时候都更加热门话题，而兴趣将在现在开始的盖亚时代增强。这些物体是晚期的B型星，通过我们的银河系以很高的速度移动，其中大多数甚至在重力上都不与我们的银河系无限。最初，与银河系中心（GC）的超质量黑洞的动态相互作用是他们唯一建议的起源。然而，与此同时，发现越来越大的高速恒星恒星并非起源于GC，因此挑战了这张照片。这些恒星是所谓的失控恒星的极端情况，这是一个众所周知的运动型奇特的恒星，可以通过恒星簇中的动态相互作用或通过破坏二进制系统的超新星爆炸来驱逐其环境。还可以认为可能是大型麦哲伦云或破坏的矮卫星星系中的外乳外的起源。在过去的几年中，我们的工作揭示了失控的明星和HVSS之间的牢固联系。因此，试图理解一类恒星也需要了解另一个类。因此，我们将研究项目扩展到了广泛的高速恒星。该项目的目的是了解大量失控和HVSS的起源和性质。这需要定量光谱和天体/运动学分析的结合。改进的模型气氛和我们团队中得出的新型光谱诊断工具应适用于高保真光谱，部分是手头。 Gaia天文统计将是该项目的骨干。可以使用这些数据来改善银河系质量模型，并将恒星轨迹追溯到其原产地。此外，可以建立一个完整的高速恒星样品来测试种群合成模型。将通过化学标记与Gaia天文学的信息相结合来确定原产地以及弹出机制。